fulton



Dec. 2, 1 4- Re. 15,957

K. H.-FULTON PROCESS OF PRODUCING CELLULAR RUBBER Original Pued may 6, 1920 Innuendo:-

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Be it known thatLKam. H. Fourozv, a citizen of the United States, residing-at Pittsburgh. in the county of Alleghen and State of Pennsylvania, have invente certain new and useful Improvements in Processes of lmducing (.ellular Rubber, of which the followin v is a specification.

The invention relates to a process of producing cellular material.

It is an object of the invention to provide a process for reducing cellular rubber, having a multitu e of separate gas bcarin cells arranged throughout the body thereo It is a further object of the invention to provide a recess wherein relatively soft cellular ro er articles, or relative] hard cellular rubbermay be produced or use in various fields The invention is based on the discovery that certain granular substances when incorporated in a bod of rubber and subjected to the action 0 a gas under pressure, p the characteristics of absorbing or occluding in the voids or interstices of the granules a preciable quantities of the gas without e ecting a change in the size or formation of the granules. If the material, while still subjected to the gas under pressur is given a vulcanizing treatment, the rubber will be vulcanized around the infinite number of minute gas bearing granules formin coatings or envelopes for the granules. he gas occluded in the granules does not escape during the vulcanizing treatment which is carried on in the presence of the gas under pressure, and after the vulcanization the material is cooled while still under gas pressure to revent the liberation of the occluded gas. 0 form the cellular material the vulcanized product is then again heated when the gas pressure has been released, the occluded gas of each granule then escaping or being released expanding the elastic material formin a coating therefor, thereby producing in t e body an infinite number of separate gas cells. The formation of each cell is produced by the releasing of the occluded gas of the granular particle, which assumes a volume several times of that of the original particle t y pa ng the cell an apprecia le mm so. clam.

extent which may be controlled-by the pm sure of the gas when the particles are first subl ficted to the action thereof. v

e final volume of the cellular rubber depends upon the number of cells. formed therein, and also I: n the amount of gas in each cell. It wi be apparent that'the granular material is intimatelfv mixed with the rubber, and the'number o oells'is equal to the number of particles of the granular material employed in the original mixture.

In carrying out the present process I preferabl intimately mix raw Para rubber with a su cient quantity of sulphur to b about vulcanization, and the finel divid granular material which is pre erabl a material such as activated charcoal. This material is commercial! manufactured by the dry distillation of ense vegetable mater1al,such as cocoanut shells, peach kernels, and the like and I have discovered that it um: the characteristic of absorbing or occluding relatively large quantities 0 gas when subjected thereto under pressure. The material is preferably comminuted orpulverized to a very fine mesh, as for example, a hundred mesh, and when thoroughly mixed with the raw rubber is shaped'into a desired form depending upon the use of the cellular rubber and subjected to the action of an inert gas under pressure. Various forms of gas may be used, but I have found that an inert gas such as nitrogen is highly eflicient in performing the process.

When the mixture is thus shaped the material is introduced to a receptacle which is sealed or formed in any convenient manner to prevent the escape of gas therefrom, and the inert gas such as nitro en is then introduced to the receptacle. he gas is readily occluded by the charcoal and finds lodgment in each of the minute voids or interstices therein throughout the infinite number of granules, but the occluded gas does not efl'ect a change in shape or size of the mass in any way. The as thus comes in direct contact with the rub er mass, and enters the activated charcoal as described above. After being subjected to the action of the gas for the desired period, the rub: a is th n ulcan z by je t g e same to the netmsary heat treatment,- attention being called to the fact that during the vulcanization of the rubber the premure of the inert is maintained, and also after vulcanization the vulcanized mass is cooled in the presence of the nitrogen gas still maintained in the container at its original pressure to prevent the charcoal from giving up this occluded gas when the pressure is later released. It will be observed that by maintaining the gas pressure during the vulcanization of the rubber, and also after vulcanization, and while the mass is being subjected to a cooling action the envelopes or skins of rubber surrounding each particle-arc permitted to harden or congeal to "event the escape or release of the occludml gas of each particle before the gas ressure maintained m the container is recased.

When the mass has been cooled after its vulcanization the gas prtssure is then released, and to the vulcanized rubber enough heat is then applied to cause the particlts of charcoal to give up all the occluded gas. This occurs in view of the. fact that during the second heating there is no gas pressure to rohibit the occluded gas from escaping mm the charcoal, each particle of which becomes the nucleus of a small gas cell. The heating of the vulcanized rubher when the pressure has been released,

causes the occluded gas, to be driven or released from the particles of charcoal, the volume or size of each particle of charcoal being exceedingly small as compared with the volume of occluded gas. The discharged gas swells this confining envelope or cell which assumes a size several times that of the original cell. It will be understood that by the provision of the infinite number of particles of charcoal, a corresponding number of cells is formed in the rubber, and that each cell is individually sealed. The resulting mass of cellular rubher is of the same configuration as the original material prior to its beating and vulcanization, but greatly increased in size in all dimensions because of the formation of the multitude of gas cells.-

It has been found that the size which the original rubber mass is to assume when in a cellular form depends of course in part upon the number-of cells formed by the granular particles of charcoal, and the amount of gas confined in each cell; The number of cells. is as before stated, equal to the number of charcoal particles used in the mixture. while the size of each cell depends upon the pressure of the gas when the material is first subjected to its action.

The greater the pressure, manifestly more gas is occluded in the particles thereby form' a larger cell when the occluded gas Y is released by the final heat treatment,

While the cellular material may be formed from the composition of suhstanm-s above described when used in various 1 mmtitles, I have found that a highly e cicnt cellular rubber can be produced by the employment of activated charcoal to the extent of approximately three to five per cent of the total of the other ingredients, that is the raw rubber and its vulcanizing agent. which may be sulphur, etc. The quantity of sulphur may ran e from live to fifteen per cent for the pri notion of good results, andinstead of sulphur antimony sulphide, sulphur or mixtures of sulphur and antimony sulphide, and many other vulcanizing agents or accelerators may be employed.

In carrying out the present process no particular form of apparatus need essentially be employctib but for. the sake of clcaruess I have disclosed in the accompanying drawing a type of apparatus which may be successfully employed to support the process. This apparatus is simply shown for the purpm o illustration, and not for limitation, and I wish it'to be distinctly understood that the process is one that is susceptible of being carried into use by many forms ofap aratus widely 'difi'erent from that discl in the present drawing forming a )art ofthis application.

In t e drawing Figure 1 represents a section view through the apparatus.

Referring now more particularly to the drawing wherein like reference characters indicate corresponding parts the numeral 1 designates a gas tight cylinder or container which may be of any convenient sha and size. This container is provided wit a removable closure 2.

The top 2 is united to the body of the container by means of the fastening devices 4 to form a scaled connection between the container and its closure, :1 suitable packing or the like being employed if desirable. The container 1 is also formed by the provision of a spaced wall 5 with a jacket 6 for receiving the heating and cooling agent.

Leading to the container 1 is a gas feeding pipe 7 controlled by the valve 8, the pipe leading from the suitable gas supply and 1 adapted to convey gas to and from the conta ner under a regulated andvarml'de pressure. The material to be treated consists of the mixed rubber. vulcanizing agent and the multitude of granular particles of activated charcoal which has been kneaded m shaped to the desired. configuration.

be shaped material is then placed in the container 1 and subjected to the action of the inert gas entering the container under pressure through the feed pipe 7. This gas is occluded or absorbed in the multitude of charcoal particles in the material, entering the voids or interstices thereof. the quantity of gas being absorbed depending upon the.

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ressure of the. as entering the container. be material is t n subjected to a vulcanizing temperature by the introduction of a heating medium, which may steam, water and the like conveyed to the jacket 6 by the feed pipe 9 and drained out through the pipe 11. The desired vulcanizin temperature is then maintained for t pro r period during which time the materia is still being subjected to the action of the inert gas under pressure. After the rubber has been. vulcanized the gas is still maintained imder ressure-inthecontainer 1 and a cooling me ium introduced to the jacket through the 12. his coo ing medium serves to revent the escape of the gas. from the particles of charcoal when the pressure is later released, forming tenacious envelopes surrounding each particle of charcoal which is later to constitute a gas cell.

When the cooling has progressed to the desired degree, the cooling medium is discharged from the jacket 6 and the gas pressure in the container 1 released until the material is subjected to an atmospheric pressure. The mass is then again heated b the introduction of a heating agent throng the feed pipe 9, to a temperature approximately 200 degrees Fahrenheit for a period of sev- 'eral; hours, which causes the particles of charcoal, each individually encircled or enclosed by an envelope or film of the rubber to release its occluded gas, and as the size of each article of charcoal is so small as compared with. the volume of'occluded gas absorbed thereby, the envelope surrounding the occluded particles is caused to swell by the suspending gas several times that of its origina size. It will be observed that this last heating step is performed while the material is no longer under the action of the ucts a'd made,

excess of sulphur to carry the vulcanization to a completion. The gas is of course occluded in the particles during this vulcanization, and subsequently released, forming a hard cellular rubber mass of high tensile strength which may be fashioned in the form of boards and the like, applicable for use as a hard insulating material for linings for refrigerators, refrigerator cars and-the like. In producing the hard vulcanized cellular rubber of this character, the vulipe 10, and out through pipe final heating to release the canization is not carried to completion when the article is first subjected to heat, but merely to a stage to produce a'soft cellular rubber. After this preliminary heating or vulcanization the material is again subjected to the action of. a vulcanizing temperature until complete vulcanization has taken place. To obtain boards or'the like havingrelatively smooth surfaces, the final vulcanizing step is referably' accomplished in a press providing smooth surfaces.

To providea soft cellular article, or cellular rubber which-is ve J spongy, a mixture of Para and balata ru rs is used, mixed with the proper quantities of sulphur or like vulcanizing agent and the granules of,

charcoal. I This material is then subjected to the treatments described in defining the main process and the articles produced are particularly useful as heat insulating, and-- water-proofing materials, upholstery, mattresses, and the like.

The present process also contemplates the production of tire fillers or like articles which naturally must possess a great amount of resiliency. In manufacturin tire fillers having a thickness of several inc es or more it has been found necessary that during the shaping of the original mixture of Para and balata rubbers and the other ingredients to, insert numerous continuous fibrous-filaments in the original rubber mixture. These filaments run from endto end of the mixture, and serve to provide passageways for the inert gas to permeate the multitude of the charcoal particles distributed through-v out the body of the mixture. This is of come in contact with and be absorbed or occluded in the activated charcoal particles which lie in the body of the filler. The mass is then vulcanized while under the infiuence of the gas pressure and cooled before the gas pressure is released. Before the as occluded in the charcoal particles the filer is preferably placed within a tire shoe mounted upon a second heating action. This causes the occluded gas tobe driven from the charcoal particles and aconsequent expansion of the course required in order that the gas may ill] rim and the entire assembly subjected to the filler so as to completely fill the interior'of" the tire shoe, because the pressureof the nitrogen has been released.

In the foregoing specification I have only described a few of the uses of the material produced by this process, but it: will of course be understood that the process is susceptible of producing materials which are useful and applicable in unlimited fields.

Having thus described my invention, what I claim is:

1. The process, of producing cellular rubber, comprising mixing rubber with gas occluded particles, in subjecting the mixture to in finally permitting the occlu ed the presence of gas under pressure to be absorbed by said gas occluded particles, in vulcanizing the material while being subjected to the gas pressure, .in allowing the material to then cool, and in finally heating the material to cause the occluded to be discharged from the articles formmg in the material a multitudg of gas cells.

2. The process of producing cellular rubber, comprising the intermixing of raw rubher with divided granular material sus-' ceptible of'occluding as, in subjecting the mixture to the action 0 a gas under ressure wherebv the granular particles ude appreciable quantities of the gas, in vulcanizmg the material while still being subjected to. the action of the gas under ressure, and

granular particles to be discharg to form in the rubber body a multitude of gas bearing cells by subjecting the same to the heat treatment in the absenceof the gas pres sure.

3. The process of manufacturing cellular rubber, comprisin the mixin of raw rubber of finely divi ed activate particles, in

subjecting the material to the action of an inert gas under pressure to be absorbed by the activated particles, in vulcanizing the material to form envelopes surrounding the granular particles having occluded gas, and inthenheating the material after the gas pressure has been released to cause the occluded gas to be discharged from the particles for expandin the formed 'envelopes, and producing in t e mass a multitude of separated gas cells. v 1 4. The process of manufacturing cellular rubber, consisting in introducing to, raw rubber a finely divlded granular material SS-' material, in absorbing in the particles a gas,

in vulcanizing the material to'form coatings surrounding the comminuted s bearing particles, and in then-heat1ng t e material to cause the gas contained in the particles to be discharged therefrom producin in the rubber a multitude of separated gas aring cells.

6. The process of manufacturing cellular rubber, comprising the intermixing' of finely divided granular material with raw rubsof theher, in subjecting the intermixed material to the action of an. inert gas under a variable regulatable pressure to cause the granular particles to absorb a Quantity of the gas, in

then subjecting the material to a vulcanizing tem rature in the presence of the inert an or pressure, in coolin the material a rvulcanization while sub ected to the inert gas under prewure and in finally again eating the, material when the pressure of the inert gas no longer exists to cause the occluded as of the granular articles to be discha e5 tude 0 gas beari cells.

7. The process 0 manufacturing cellular rubber, which consists in mixin with a granular activated materia in subjecting the mixture to the action of a gas under pressure to cause the granular material to absorb as, in vulcanizing the mixed substances whi e under pressure, 1n cooling the material, in releasing the gas pressure after cooling, and in then heating the material to cause the occluded gas to be 'discharged from the granular particles forming'a multitude of rubber cells.

8. The rocess of producing cellular rubber, whic consists in mixing with rubber forming material gas occluding particles, in vulcanizing the mixture and in allowing forming in the m bera multi-.

rubber the same to then cool, and in finally heating the material when in a 0001 state to cause the occluded gas of the particles in the material to be released forming therein a multitude of non-communicating gas cells.

9. The lprocess of producing cellular rubber whic consists in mix the rubber and gas occluding particles, 1n subjecting the mixture to the presence of gas, in vulcanizing the mixture, in allowing the vulcanized product to cool, and in finally heating the material to cause the particles to give up through occluded gas forming in the malilterial a multitude of non-communicating ce s.

10. The process of manufacturin cellularv rubber, consistin in mixing rub 'r with activated charcoa in granular form, in subjecting said mixture to the action of gas under pressure to cause the activated charcoal to absorb substantial quantities of said gas, in vulcanizing the mixed substances while maintained under gas pressure, in releasing the pressure after vulcanization, and in dischar ing the occluded gas from said activated c iarcoal particles by reheating the mass, to form in said rubber mass a multitude of gas bearing cells.

11. The process of manufacturing cellular rubber consisting in mixing rubber with activated charcoal, in subjecting the mixture to the action of gas under pressure to cause said charcoal to absorb the gas, in vulcanizing the mixed substances, and in discharging the occluded gas from said activated.

ber, consisting in mixing raw unvulcanized rubber with comminuted activated charcoal, subjectin said mixture of charcoal and rubber to t e action of gas under a superatmos heric ressure before vulcanization of e rub r to cause the activated charcoal to absorb substantial quantities of said gas, in vulcanizin said mixed ubstance while under sai pressure, and in then releasing said pressure to cause the occluded gas in the vulcanized rubber to form therein a series of gas bearing cells.

In testimony whereof I aflix my signature.

KARL H. FULTON. 

